Pressure rheostat



Aug. 7, 1923. v 1,464,025

H L. BRADLEY PRESSURE RHEOSTAT Filed July 13 1922 2 Sheets-Sheet 1 Patented Aug. 7, 1923. I

UNITED STATES PATENT OFFICE.

mm L. BRADLEY, or MILWAUKEE, Wisconsin, assmnon. BY misun ASSIGN- nnn'rs, To run RELIANCE conrmr, or mnwauxnn, isconsin, a cannon- T1011 OF WISCONSIN.

PRESSURE RHEOSTAT.

Application filed July 18, 1922. Serial No. 574,795.

T all whom. it may concern .1

Be it known that I, HARRY L. BRADLEY, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Pressure Rheostats, of which the following is a specification.

This invention relates to a pressure rheostat.

The rheostat to which this invention particularly applies has a resistor the resistance of which is variable under pressure and means for, varying the pressure applied I thereto. v

Among the objects of the invention is to i provide a rheostat the resistance of which may be varied steadily and smoothly;

' nother object is to provide a r eostat which' is efiicient and durable and which may be easily and quickiy adjusted to obtain s difl'erent resistance values.

Another object is to provide a rheostat having a compression resistor and resilient x'neans for smoothly varying the pressure applied thereto.

f' having a pair of compression resistors the Fig. 1 is a transverse vertical section through the pressure rheostat.

Fig. '2 is a front elevation from line 2-2 of Fig. 1.-

Fig. 3 1s a plan of the cam disk of the actuator.

Fig. 4 is a side elevation thereof. Fig. 5 is a side elevation thereof taken at 90 from that of Fig. 4.

nother object is to provide a rheostat.

resistance of which may be simultaneously Fig. 6 shows curves illustrating how the resistance of one resistor increases and that of the other decreases while the combined resistance remains substantially constant.

Fig. 7 shows the pressure rheostat employed to vary the voltage impressed on the anode of an electronic valve detector.

Fig. 8 shows the pressure rheostat employed as a voltage divider.

The rheostat comprises resistors 1 and 2 and an actuator 3 for causing the simultaneous decrease of the resistance of one and the increase of the resistance of the other resistor.

Each resistor is made of a plurality of contacting electrodes 4 of graphite or other suitable material. The electrodes may take the form of fiat disks. is thicker than the intermediate disks and may be made of metal silver plated to insure good electrical contact with co-operatmg parts.

The resistors are located in spaced pockets of an insulated casing 6 made of porcelain or other suitable material. The casing is ordinarily held in the position shown in Fig. 1 so that the resistors are horizontally disposed with the disks thereof arranged vertically.

The inner end disk 5 of each resistor is in contact with the head of the rivet 7 by which the terminal 8 is fastened to the easing 6. The rivet 7 is internally threaded to receive an adjusting screw 9.

The inner end of the screw 9 engages the inner end disk 5. By means of the screws 9 the initial pressure onthe resistors may be adjusted to obtain the proper initial resistance thereof. The screws 9 may be locked in adjusted position by lock nuts 9'.

The actuator 3 comprises a rotatable cam disk 10 acting on axially movable members interposed between the ends of the resistors and the cam disk.

The rotatable cam disk 10 is *fistened to a hub 11 fixed to a spindle 12.

The spindle 12 is rotatably mounted in an externally shouldered sleeve 14 supported by the casing 6 and cover 13 therefor.

The cam disk 10 is provided with cam faces 15.

The cam faces 15 co-operate with two-laxially movable plungers 16 recessed to receive Each end disk 5 coil springs 17. The inner end of the coil springs rests against the outer end disk 5 of the resistors.

The springs 17 maintain the resistors under a certain degree of compression at all times, and assist the cam actuator in causing the steady and smooth variation of the resistance of the resistors. The springs 17 due to the resiliency thereof, absorb irregularities in pressure resulting from any irregular operation of the actuator.

Each plunger 16 is slida'bly mounted in a bushing 18 carried by the cover 13.

The cam disk is provided with shoulders 19 located approximately 180 apart which co-opera'te with a stop pin 20 projecting from the cover 13 to limit the rotative movement of the cam disk.

Thus the cam disk may be rotated through approximately 180.

The cam disk is so formed that it is thinnest at the point 21 and gradually increases in thickness to a point 22, 180 therefrom. Thus during the rotative movement of the cam disk the pressure on one resistor increases while that on the other resistor decreases. 7

While the resistance of one resistor .increases and that of the other decreases the total resistance of the two resistors remains approximately constant for every position of the actuator.

In order to assist in holding the actuator in any adjusted position, the inner end of the spindle 12 is provided with a bowed spring 40, the edges of which are held against the casing 6-by an adjustable nut 41 and a lock nut 42 on the spindle.

The spindle is provided with a knob 23 for operating the actuator.

The cover 13 may be fastened to the casing 6 by means of rivets 24 or other suitable fastening means.

The cover is provided with mounting lugs 25 so that by means of suitable co-operating screws and spacing sleeves (not shown) the voltage divider may be securely fastened to a panel 26 or other support.

Electrical contact between the two resis-' tors is made through the springs 17 the axially movable plungers 16, bushing 18, cover 13 and cam disk 10.

The pressure rheostat has, in addition to the two terminals 8, an intermediate terminal, so that connection may be made to the rheostat between the resistors thereof. The cover of the casing may serve as this intermediate terminal.

Fig. 6 shows two resistance curves illustratingthe variation in resistance of the two resistors for the politions of the cam actuator, curlve a representing one resistor and curve 6 the other. The ordinates represent resistance and the abscissae the positions of the actuator.

When the actuator is at the limit of its movement in one direction the resistance of one resistor is at its high value and that of the other at its low value. When the actuator is at the other limit of its movement, the conditions in the resistors are reversed. The total resistance of the two resistors however remains approximately constant for all positions of the actuator.

Fig. 7 shows a radio telephone system in which the pressure rheostat is employed to vary the voltage impressed on the anode of the electronic valve detector.

The radio telephone system comprises a grounded aerial 30 connected through a transformer 31 and an electronic valve detector 32 to telephone receivers 33.

The electronic valve 32 has a cathode 34 heated by current supplied from battery 35, an anode 36 and a, supplemental anode 37.

The primary of the transformer 31 is connected to the cathode 34 and supplemental anode 37.

The telephone receivers 33, in series with a battery 38, are connected to the cathode 34 and the anode 36.

The pressure rheostat 39 is connected between batteries 35 and 38, so that a voltage higher or lower than that of battery 38 may be impressed upon anode 36.

The two resistors of the rheostat are connected in series and across the battery 35, while the intermediate terminal is connected to one pole of battery 38.

...By varying the resistance of the resistors,

the voltage from battery 35 delivered to the anode circuit may be varied.

When the rheostat actuator is in its midposition, the voltage impressed upon the anode 36 will be that of battery 38.

If the actuator be moved in one direction from its midposition, the voltage impressed upon the anode 36, Will be increased, while if moved in the opposite direction the impressed voltage will be decreased.

Fig. 8 shows a radio telephone system of the same general type shown in Fig. 7, but with ,.this diiference. the rheostat is employed as a voltage divider and is so connected that current for heating the cathode 34 of the electronic valve is supplied from battery 38, thereby eliminating the usual cathode battery.

The resistors are connected in series across battery 38, and the intermediateterminal is connected to one end of the cathode 34. The other end of cathode 34 is connected to the negative pole of battery 38.

By varying the resistance of the resistor connected in parallel with the cathode 34, the amount of current supplied to the cathode may be varied.

The use of a pressure rheostat having a plurality of sets of contacting electrodes whose resistance varies under pressure, allows the resistance to be varied smoothly, evenly and steadily throughout the range required for regulation of the electronic valve.

The invention set forth herein is, of course, susceptible of other embodiments and adaptations.

The invention claimed is:

1. In a pressure rheostat the combination of a pair of' resistors the resistance of which is variable by variation in pressure, and an actuator for simultaneously decreasing the resistance of one resistor and increasing the resistance of the other. i

2. In a pressure rheostat the combination of a pair of resistors each composed of material whose resistance varies under pressure, and an actuator for simultaneously compressing one resistor and decompressing the other. I

3. In a pressure rheostat the combination of a pair of resistors each having a plurality of contactin electrodes, the resistance of each resistor loeing variable by variations in pressure between the electrodes thereof, and an actuator for simultaneously increasing the pressure between the electrodes of one resistor and decreasing the pressure between the electrodes. of the other resistor.

4. A pressure rheostat comprisin a pair of resistors the resistance of whic varies under pressure,'each resistor being formed of a plurality of contactin graphite disks, and a. cam actuator forsimu taneously compressin one resistor and decompressing the other.

5. A pressure rheostat comprising two resistors the resistance of which varies under pressure, a casing therefor, a cover for the casing, a rotatable spindle carried by the casing, a cam disk mounted on the spindle, and an axially movable member for each resistor interposed between one end thereof and the cam disk so that increasing pressure is imposed on one resistor and decreasing pressure on the other when the spindle is rotated.

6. A pressure rheostat comprising two resistors the resistance of which varies under pressure, a casing therefor, a cover for the casing, a rotatable spindle carried by the casing, a cam disk mounted on the spindle, an axially movable member for each resistor interposed between one end thereof and the cam disk so that increasing pressure is imposed on one resistor and decreasing pressure on the other when the spindle is rotated, and a stop for limiting the rotary movement of the cam disk.

7. A pressure rheostat comprising two resistors the resistance of which varies under pressure, a casin therefor, a cover for the casing, a rotatabe actuator carried by the cover and having a cam for simultaneously decreasing the pressure on one resistor and increasing the pressure on the other, and an decreasing the pressure on one resistor and increasing the pressure on the other, an axi'ally movable yieldable member for each resistor interposed between one end thereof and the cam, and a stop for limiting the rotative movement of the actuator.

9. In a pressure rheostat, the combination of two resistors which are steadily and smoothly variable by variations in pressure, resilient means for varying such pressure, and a cam actuator co-operating with such resilient means whereby one resistance increases while the other decreases.

10. A pressure rheostat coinprising two resistors, each made of a plurality of contacting electrodes, resilient means for varying the pressure between the contacting electrodesv and means for so varying the tension of the resilient means that the resistance of one resistor increases whilethat of the other decreases. I f

11. A pressure rheostat comprising two resistors, each made of a plurality of contacting electrodes and the resistance being variable by variations in pressure between the electrodes thereof, resilient means for varying such pressure, an actuator common to the resistors to so vary the tension of the resilient means that the resistance of one resistor increases while that of the other decreases, and means for independently adjusting the pressure between the electrodes of the respective resistors.

12. In a pressure rheostat, the combination of two resistances, each being steadily and smoothly variable by variations in pressure, and means to simultaneously increase such pressure on one resistance and decrease it on the other.

18. A pressure rheostat comprising a pair of resistors the resistance of which varies under pressure, means for adjusting the initial pressure on said resistors and means for simultaneously compressing one resistor and de-compressing the other.

14. In a pressure rheostat the combination of a resistor composed of material the resistance of which varies under pressure, an insulating casing therefor, means for varying the pressure on said resistor comprising a spring pressed plunger and means for actuating said plunger.

15. A pressure rheostat comprising a casing, a resistor therein whose resistance-varies under pressure, .a cover for said casing, a

plunger for compressing said resistor extending through said cover, and means engaging the outwardly extending end of said plunger for actuating the same.

16., A pressure rheostat comprising an insulating casing, a resistor therein the resistance of which varies under pressure, a terminal for one end of said resistor comprising a screw passing through said casing and against which said resistor is compressed and a metallic cover for said casing providing a second terminal for said resistor.

17. A pressure rheostat comprising a casing, a resistor therein the resistance of which varies under pressure, a cover for said casing, a plunger for compressing said resistor extending through said cover, means for engaging the outwardly extending end of said plunger for controlling the compression of the resistor and a rotary member for actuating said means.

18. A pressure rheostat comprising a casing, a resistor in said casing the resistance of which varies under pressure, a terminal in one end of said casing against which said resistor is compressed, a plate closing the opposite end of said casing and forming a second terminal, compression means for said resistor forming electrical connection between said cover plate and the resistor and a rotary member secured to said cover plate for actuating said compression means.

19. In a pressure rheostat the combination of two resistors which are steadily and smoothly variable by variations in pressure, resilient means for each of said resistors and a cam actuator co-operating with said resilient means to vary the pressure on said resistors.

20. In a pressure rheostat the combination of a resistor-the resistance of which varies under pressure, a casing therefor, an actuator for said resistor comprising a spring pressed plunger and a rotatable disc provided with a cam face engaging said plunger.

In witness whereof, I have hereunto subscribed my name.

. HARRY L. BRADLEY. Witnesses:

ARTHUR J. Baum, RICHARD FISHBACH. 

